U.S. patent number 7,162,310 [Application Number 10/842,888] was granted by the patent office on 2007-01-09 for flat wire helix electrode used in screw-in cardiac stimulation leads.
This patent grant is currently assigned to Pacesetter, Inc.. Invention is credited to Phong D. Doan.
United States Patent |
7,162,310 |
Doan |
January 9, 2007 |
Flat wire helix electrode used in screw-in cardiac stimulation
leads
Abstract
An implantable endocardial lead for use with a cardiac
stimulation device includes an active fixation helix disposed at
the distal end of the lead. The helix is constructed of flat wire
having a non-circular cross section. The helix may be fixed or
movable between a retracted position fully within the lead and an
extended position advanced beyond the distal end of the lead.
Inventors: |
Doan; Phong D. (Stevenson
Ranch, CA) |
Assignee: |
Pacesetter, Inc. (Sylmar,
CA)
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Family
ID: |
34941194 |
Appl.
No.: |
10/842,888 |
Filed: |
May 10, 2004 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20050251240 A1 |
Nov 10, 2005 |
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Current U.S.
Class: |
607/127 |
Current CPC
Class: |
A61N
1/0573 (20130101); A61N 2001/0578 (20130101) |
Current International
Class: |
A61N
1/05 (20060101) |
Field of
Search: |
;607/126-128,131
;600/375 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0042551 |
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Dec 1981 |
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EP |
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0 092 797 |
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Nov 1983 |
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EP |
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0 092 798 |
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Nov 1983 |
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EP |
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0709111 |
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May 1996 |
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EP |
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0709111 |
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Nov 1997 |
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EP |
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Primary Examiner: Evanisko; George R.
Claims
What is claimed is:
1. An implantable endocardial lead having a longitudinal axis and
extending between proximal and distal ends, the implantable
endocardial lead being for use with a cardiac stimulation device
and comprising: an electrical conductor within the lead extending
between proximal and distal ends; and an active fixation electrode
comprising an electrically active helix coupled to the distal end
of the electrical conductor, the electrode being constructed of
flat wire having a non-circular cross section; wherein the cross
sectional dimension of the electrode wire is greater in the
direction of the longitudinal axis of the lead than in a direction
transverse of the longitudinal axis of the lead; and wherein the
cross sectional dimension of the electrode wire is in the range of
about 0.002 inches.times.0.008 inches to about 0.005
inches.times.0.015 inches.
2. An implantable endocardial lead as set forth in claim 1 wherein
the electrode is constructed of flat wire having a quadrilateral
cross section.
3. An implantable endocardial lead as set forth in claim 1 wherein
the electrode is constructed of flat wire having a partially
elliptical cross section.
4. An implantable endocardial lead as set forth in claim 1 wherein
the electrically active helix is movable between a retracted
position fully within the lead and an extended position advanced
beyond the distal end of the lead.
5. An implantable endocardial lead as set forth in claim 1
including: an insulation sheath covering the electrical conductor
defining an internal chamber extending from the proximal end to the
distal end; and an electrical connector being coupled to the
proximal end of the electrical conductor.
6. An implantable endocardial lead as set forth in claim 5 wherein
the insulation sheath is composed of at least one of silicone and
polyurethane.
7. An implantable endocardial lead as set forth in claim 1 wherein
the outer diameter of the electrode is in the range of about 3 fr
to 9 fr.
8. An implantable endocardial lead comprising: a lead body; an
electrical conductor extending within the lead body; at least one
electrode mounted on the lead body and connected to the electrical
conductor; and an active fixation helix disposed at the distal end
of the lead body, the active fixation helix being constructed of
flat wire having a non-circular cross section; wherein the cross
sectional dimension of the flat wire is greater in the direction of
the longitudinal axis of the lead than in a direction transverse of
the longitudinal axis of the lead; and wherein the cross sectional
dimension of the flat wire is in the range of about 0.002
inches.times.0.008 inches to about 0.005 inches.times.0.015
inches.
9. The implantable endocardial lead of claim 8 and further
comprising an electrical conductor connected to the active fixation
helix, wherein the active fixation helix is electrically
active.
10. The implantable endocardial lead as set forth in claim 8
wherein the active fixation helix is constructed of flat wire
having a quadrilateral cross section.
11. The implantable endocardial lead as set forth in claim 8
wherein the active fixation helix is constructed of flat wire
having a partially elliptical cross section.
12. The implantable endocardial lead as set forth in claim 8
wherein the active fixation helix is movable between a retracted
position fully within the lead and an extended position advanced
beyond the distal end of the lead.
Description
FIELD OF THE INVENTION
The present invention relates generally to implantable stimulation
leads for use with an implantable pulse generator such as a cardiac
pacemaker or defibrillator and, more specifically, to such an
implantable stimulation lead with the capability of selectively
anchoring an electrically active helix electrode of improved design
at a desired site when the lead is fixated in the heart.
BACKGROUND
Currently, known extendable/retractable screw-in implantable
stimulation leads have an electrically active helix electrode. The
helix electrode may be capable of extension and retraction from the
header by being directly connected to the connector pin/distal coil
subassembly. Turning of the connector pin results in the extension
or retraction of the helix electrode from the header. In order for
the helix to be extended or retracted, a thread/screw mechanism is
required. The helix electrode is used as a threaded screw which
turns against a thread post in the header. As the helix rotates, by
turning of the connector pin, it engages the thread post, which in
turn drives the helix into and out of the header.
Leads are also known which employ a fixed extended electrically
active helix electrode and the invention is applicable to such
leads as well.
Traditionally, the helix electrode of either fixed screw-in or
extendable and retractable screw-in leads is made out of a round
wire. The size of the wire should be small enough so as not to
severely damage the heart tissue but thick enough to achieve good
fixation while being visible under fluoroscopy. In addition, the
outer diameter of the helix electrode should be sufficiently large
to achieve a good and less traumatic fixation but not too small to
core out the heart tissue. Currently, the appropriate range of the
helix wire diameter is between about 10 mils (0.010 inches) and 13
mils (0.013 inches) and the outer diameter of the helix wire
desirably ranges from about 0.040 inches to 0.070 inches. The outer
diameter of the helix and the helix wire diameter must be balanced
in order to create a first class helix electrode. In order to
downsize the distal tip of a screw-in lead for a smaller lead,
besides other design considerations at the distal tip, the helix
wire size and outer diameter could be reduced to a certain extent.
However, further reduction of the helix wire size or helix outer
diameter would compromise the performance of the helix electrode in
terms of electrode pacing threshold and helix visibility. The
invention allows for more design options for the tip of a smaller
lead without compromising helix performance.
Typical of the known prior art is U.S. Pat. No. 4,860,769 to
Fogarty et al. which provides for an implantable defibrillator
electrode including a flexible insulated guide terminating in a
flexible distal portion which includes a conductive element and is
of a predetermined configuration, such that it may be extended to a
linear configuration by the application of a concentric or axial
force and upon the termination of such force assumes the
predetermined configuration. The conductive portion of the
electrode may be a spiral of flat wire helically wound on a
generally cylindrical, non-conductive stem.
Another example of the prior art can be found in U.S. Pat. No.
4,920,979 to Bullara which discloses a circumneural electrode
assembly including a supportive flexible and insulating matrix
formed into two oppositely directed helical portions which are
centrally joined, and have free outer ends. The helical portions
extend circumferentially at least one full turn, and preferably
about one-half additional turn, for a total extent in the range of
360 degrees to 720 degrees. A thin and flexible conductive ribbon,
preferably of surface-roughened platinum, is secured to the inner
surface of one of the helical portions, and multiple electrodes can
be provided on one or both portions. A connecting wire or cable
extends from the electrode and matrix for coupling to an electronic
package which is normally implanted elsewhere in the patient's
body.
Still another example of the prior art can be found in U.S. Pat.
No. 5,964,702 to Grill, Jr. et al. which discloses a helical nerve
cuff electrode which is provided for encircling a nerve trunk or
other body tissue with at least one medication or electrically
energy conductive member disposed along the length of the helical
cuff. The cuff includes a self-curling sheet of non-conductive
material laminations which are collectively self-biased to curl
into a tight helix.
SUMMARY
An implantable endocardial lead for use with a cardiac stimulation
device includes an internal electrical conductor and an active
fixation electrode with a coaxial electrically active helix coupled
to the distal end of the electrical conductor for effecting
penetration into the myocardial tissue. The electrode is
constructed of flat wire having a non-circular, such as
quadrilateral or elliptical, cross section. The electrically active
helix may be fixed or movable between a retracted position fully
within the lead and an extended position advanced beyond the distal
end of the lead. An insulation sheath of silicone or polyurethane
covers the electrical conductor defining an internal chamber
extending from the proximal end to the distal end and an electrical
connector is coupled to the proximal end of the electrical
conductor. With this construction, the outer diameter of the
electrode is in the range of about 3 French (0.039 inches) to 9
French (0.118 inches) and the cross sectional dimension of the
electrode wire is greater in the direction of the longitudinal axis
of the lead than in a direction transverse of the longitudinal axis
of the lead, being in the range of about 0.002 inches.times.0.008
inches to about 0.005 inches.times.0.015 inches.
Thus instead of using round wire, flat wire with a thickness
typically thinner than the diameter of the round wire, is used for
the helix electrode. It could be used for smaller diameter helix
electrodes while maintaining other critical design parameters and
potentially increasing fluoroscopic visibility of the helix due to
a wider profile of the flat wire as compared with the round,
conventional, wire.
Other and further features, advantages, and benefits will become
apparent in the following description taken in conjunction with the
following drawings. It is to be understood that the foregoing
general description and the following detailed description are
exemplary and explanatory but are not to be restrictive of the
invention. The accompanying drawings which are incorporated in and
constitute a part of this invention, illustrate one of the
embodiments of the invention, and together with the description,
serve to explain the principles of the illustrative embodiment in
general terms. Like numerals refer to like parts throughout the
disclosure.
BRIEF DESCRIPTION OF THE DRAWINGS
The foregoing aspects and other features of the present invention
are explained in the following description, taken in connection
with the accompanying drawings, wherein:
FIG. 1 is a perspective view illustrating a heart with a portion
cut away to reveal an implantable lead assembly according to one
illustrative embodiment and secured therein to a wall of the
heart;
FIG. 2 is a perspective view of an implantable lead in combination
with a cardiac stimulation device such as a pacemaker or
defibrillator;
FIG. 3 is a longitudinal cross section view of a known electrode
assembly at the distal end of the type of lead illustrated in FIG.
1, with the helical electrode in the retracted position;
FIG. 4 is a longitudinal cross section view of the known electrode
assembly at the distal end of the pacing lead with the helical
electrode in the extended position;
FIG. 5 is a detail perspective view of the distal end of the lead
illustrated in FIG. 1, with the helical flat wire electrode in the
retracted position;
FIG. 6 is a cross section view taken generally along line 6--6 in
FIG. 5;
FIG. 7 is a cross sectional view, similar to FIG. 6, illustrating
the helical flat wire electrode in the extended position;
FIG. 8 is a cross section view of a helical electrode wire
according to one illustrative embodiment having a quadrilateral
cross section; and
FIG. 9 is a cross section view of a helical electrode wire
according to one illustrative embodiment having an elliptical cross
section.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to FIG. 1, there is shown a diagrammatic perspective view
partially cut away and shown in section of a heart 10 into the
right ventricle 12 of which is inserted a body implantable lead 14
of the endocardial type according to one illustrative embodiment.
Although certain illustrative embodiments are shown in the
drawings, it should be understood that the present invention can be
embodied in many alternate forms or embodiments. In addition, any
suitable size, shape or type of elements or materials could be
used. The lead 14 of an active fixation design is attached to an
interior wall 16 of the heart 10 by means of a fixing helix 18
which engages the tissue or trabeculae of the heart.
As further illustrated, the lead 14 also includes an insulation
sheath 20 interconnecting the helix 18 secured to the interior wall
16 and an electrical connector 24 at a proximal end 26 to which can
be attached a cardiac stimulation device 28 such as a pacemaker or
defibrillator (FIG. 2). In FIG. 1, a stylet 30 is illustrated
inserted within the insulation sheath 20 and may be used to provide
rigidity to the lead 14 during insertion of the lead into the heart
10. The elongated stylet 30 extends through a lumen of the
insulation sheath 20 between a distal attachment device and a
proximal manipulating device 32. The manipulating device is distant
from the distal attachment device and may be a finger grip at a
proximal extremity of the stylet 30 provided for controlling the
introduction of the stylet into the lead 14 and its subsequent
withdrawal.
The lead 14 is designed for intravenous insertion and contact with
the endocardium and, as such, may be conventionally referred to as
an endocardial lead. The lead 14 includes coil or helically wound
electrical conductors (not shown in this view) covered with the
insulation sheath 20. The insulation sheath is preferably
fabricated of silicone rubber, polyurethane or other suitable
plastic material. At the proximal end 26 of the lead 14, the
connector assembly 24 is provided with sealing rings 34 and carries
at least one, and preferably a pair, of electrical contacts 36.
The connector assembly 24 is constructed using known techniques and
is preferably fabricated of silicone rubber, polyurethane or other
suitable plastic material. Contacts 32 are preferably fabricated of
stainless steel or other suitable electrically conductive material.
The lead 20 is constructed to include a hollow interior extending
from the proximal end 26 to a distal end 38. As earlier mentioned,
the hollow interior of the lead 14 allows for the introduction of a
stylet during implant, which is beneficial in allowing the surgeon
to guide the otherwise flexible lead from the point of venous
insertion to the myocardium.
At the distal end 38 of the lead 14 is an electrode assembly 40
which may take many different forms. For example, lead 14 may
include one or more ring electrodes for bipolar sensing and pacing,
as is well known in the art. Lead 14 may further include a
defibrillation electrode for delivering defibrillation shocks. In
these embodiments, one or more conductors extend through the lead
housing to conduct electrical energy to the various electrodes.
Furthermore, in at least one embodiment, the helix fixation member
18 may be electrically inactive, with the sensing and pacing
functions being performed by the electrode assembly 40.
FIGS. 3 and 4 depict a known construction for the distal end 38 of
the lead 14 of FIG. 1. In FIGS. 3 and 4 the helix or helical
electrode 18 is seen affixed to an advanceable electrical
interconnect 46. The electrical interconnect 46 is also
electrically connected to the conductor 48 which extends from the
distal end to the proximal end of the lead 14. The electrical
interconnect 46 thus includes a tail portion 50, to which the
conductor 48 is secured, a central shaft portion 52 and a head
portion 54. The helical electrode 18 is connected to the head
portion 54. The central shaft portion 52 of the electrical
interconnect 46 passes through a seal assembly 56. The seal
assembly 56 may include a pair of retaining rings 58 which
cooperate to secure a resilient ring seal 60. The seal assembly 56
prevents bodily fluids from penetrating into the axial void
extending through the center of the lead 14.
As also depicted in FIGS. 3 and 4, the distal end 38 of the lead 14
terminates in a sleeve 62 which is essentially a cylindrical
element having a central bore within which the helical electrode 18
is disposed and retractable. The sleeve 62 is preferably fabricated
from a biocompatible elastomeric material. The distal tip of sleeve
62 may include one or more metallic rings 64, which are useful
during implant to allow a physician to verify the position of the
helical electrode 18 relative to the metallic ring 64 in either the
extended or retracted position by the use of a fluoroscope.
Further, the sleeve 62 includes a knob 66 extending from the inner
diameter to guide the rotative advancement of the helical electrode
18. It is to be understood that techniques for implanting a pacing
lead and advancing the fixation elements are known in the art, and,
therefore, will not be discussed here.
The proximal end of the sleeve 62 is affixed to a stepped
cylindrical element 68, which is preferably formed from a
biocompatible nonconductive material. The stepped cylindrical
element 68 includes a cylindrical portion 70 which slides into the
proximal end of the cylindrical sleeve 62 and is bonded thereto.
The seal assembly 56 is located between an end-face 72 of the
stepped cylindrical element 68 and an internal step 74 of the
sleeve 62.
As further illustrated in FIGS. 3 and 4, the proximal end of the
distal assembly 36 may include a second ring electrode or sensor
electrode 76 spaced proximally of the distal tip. The ring
electrode 76 is electrically interconnected to a second conductor
78 which also extends from the proximal to the distal end of the
lead body 22 and is helically wrapped about the cylindrical
insulation containing the first conductor 48. The second electrical
conductor 78 is also preferably encased in an insulation sleeve 80.
The second electrical conductor 78 extends to and interconnects
with an electrical contact (not shown) located at the connector
assembly 28 at the proximal end 26 of the lead 14.
In FIGS. 3 and 4, a therapeutic delivery means is provided which
includes a therapeutic bullet 82 centrally disposed with respect to
the helical electrode 18, that is, along the axis of the helix. The
therapeutic bullet 82 is preferably secured to the head portion 54
of the electrical interconnect 46, and advanceable therewith. As
depicted in FIG. 4, when the helical electrode 18 is fully extended
and inserted into the myocardium upon implant, the therapeutic
bullet 82 does not extend out of the end of the sleeve 62 as does
the helical electrode 18. Although, according to the design
illustrated in FIGS. 3 and 4, the therapeutic bullet 82 is only
advanceable with the advancement of the electrical interconnect 46,
other constructions are known according to which the therapeutic
bullet is independently advanceable.
Turn now to FIGS. 5 9, which show illustrative embodiments of a
lead. The distal end 38 of the lead 14 is clearly seen in FIGS. 5
7. FIGS. 5 and 6 illustrate a modified electrically active helical
electrode 18A in its retracted position and FIG. 7 illustrates the
electrode 18A in its extended position. In this instance, the
electrode 18A is constructed of flat wire having a non-circular
cross section and, more specifically, is constructed of flat wire
84 having a quadrilateral cross section. This cross section of the
electrode 18A is most clearly seen in FIG. 8 and it will be
appreciated that the cross sectional dimension of the electrode
wire is greater in the direction of the longitudinal axis of the
lead 14 than in a direction transverse of that longitudinal axis.
The outer diameter of the electrode 18A is in a distinctly superior
range of about 3 Fr to 9 Fr. Because of the wider profile of the
flat wire, its visibility under fluoroscopy is much improved over
electrodes using wire of round cross section. Additionally, when
such an electrode is used, distinct edges 86 of the flat wire 84
provide an improved pacing threshold due to edging effect. For the
electrode 18A, preferred cross sectional dimensions of the
electrode wire 84 are in the range of 0.002 inches.times.0.008
inches to about 0.005 inches.times.0.015 inches.
In another instance, viewing FIG. 9, a further modified electrode
may be constructed of flat wire 88 having an elliptical cross
section.
It should be understood that the foregoing description merely
describes illustrative embodiments of leads. Various alternatives
and modifications can be devised by those skilled in the art
without departing from the invention. Accordingly, the invention
should be determined by reference to the appended claims.
* * * * *